Kinked wire coil shunt



July 25, 1967 D. R. VINSON 3,332,351

KINKED WIRE con, SHUNT Filed Nov. 18, 1965 2 Sheets-Sheet l INVENTOR. ,7Donald R. Vinson' ATTORNEY July 25, 1967 KINKED Filed Nov. 18, 1965FIG.3

D. R. VINSON WIRE COIL SHUNT 2 Sheets-Sheet 2' FIG.4

FIG. 5

INVENTOR. Donald R. Vinson BY fl ATTORNEY V I United States Patent3,332,351 KINKED WIRE COIL SHUNT Donald R. Vinson, Tamaqua, Pa.,assignor to Atlas Chemical Industries, Inc., Wilmington, Del., acorporation of Delaware Filed Nov. 18, 1965, Ser. No. 508,461 1 Claim.(Cl. 10228) ABSTRACT OF THE DISCLOSURE In the art of electric blastingcaps having terminally uninsulated leg wires, a shunt of coiled wireofiset in a kinked configuration about the uninsulated portions of theleg wires so that the leg wires and coiled shunt are in kinked contact.

This invention relates to a safety device for electric initiators andmore particularly to a wire coil shunt which is positioned around theuninsulated portion of lead-in or leg wires of electric initiators andkinked in position thereon.

Electrict blasting caps are known to be comprised of an elongated metalcasing in which an explosive charge is contained at one end. Two legwires are extended into the opposite end of the casing and connectedtherein by means of a bridge wire which is embedded in an explosivecomposition which is readily ignited. The terminal ends of the leg wiresfurthest from the cap are normally supplied uninsulated so as to allowfor making electrical contact to a suitable source.

It is well known that because of the uninsulated portions of blastingcap leg wires there exists an opportunity for premature or accidentalinitiation of such caps. For example, the uninsulated leg wires may comeinto contact With a live circuit or a stray electric current source.

The positioning of the present shunt on the uninsulated portion of theleg wires leading to electric initiators acts to establish a shortcircuit between the two leg wires, so that any stray electrical currentbrought into contact with one of the leg wires will not go to theinitiator and cause a premature or accidental explosion. The presentshunt is particularly adapted to be used on leg wires of electricblasting caps during the periods while they are being stored,transported and the period during which they are being handled at theblasting site prior to connecting the leg wires to an electrical sourcefor firing.

Commercial electric blasting caps are generally equipped with insulatedleg wires the terminal ends of which are not insulated for a length ofabout 1 /2 inches to about 3 inches. These uninsulated ends are providedfor connecting the leg wires to a proper electrical source forinitiation purposes. It is around this uninsulated portion of the legwires that the present shunt is positioned in a kinked or oifsetconfiguration so as to bring each leg wire into contact with the otherand into contact with the shunt. In one embodiment of the presentinvention the shunt is kinked in such a manner so as to be in positivecontact with the leg wires at points within the coiled shunt wherein theleg wires enter and leave the kinked portion and also at the point ofgreatest depression of such a shunt. In another embodiment of thepresent in vention the shunt is kinked into positive contact with theleg wires only at points within the coil wherein the leg wires enter andleave the offset portions of the kinked shunt. However, according to thepresent invention positive contact between the leg wires and the shuntmay be made at any point or multiplicity of points within the length ofthe present shunt.

The present shunt may be applied to leg wires by 3,332,351 Patented July25, 1967 threading the uninsulated portion of such wires through thecenter of a coil of wire or the coil may be formed by winding theshunting wire about the leg wires. The shunting wire coil and leg wiresthreaded therethrough are then deformed or kinked by any suitablepressure means so as to bring about the desired contact. Through the useof such kinked shunt maximum security against the shunt slipping off isachieved. The inside diameter of the present coiled shunt is suitably ofsuch diameter to accommodate the width of two uninsulated leg wires sothat there will be very little free space.

The inside diameter of the particular shunt to be used on any given legwires in accordance with the present invention is selected so that eventhough the present shunt is not compressed into positive contact withthe leg wires throughout the entire length of the shunt, it is mostlikely that the leg wires will contact the present shunt at many pointsthroughout its length.

The spiral or coil wire shunt of the present invention may be made ofany suitable metal, for example, copper, lead, aluminum or any otherconductive metal which can be formed into wire and which is capable ofbeing kinked around leg wires and remaining in that configuration. Thepresent shunts may be of any length that are practical for applicationaround the uninsulated portion of the leg wires of a blasting cap. Forexample, the present shunts may be from about /2" to about 3" in length.

For greatest protection it is recommended that the present shunt bepositioned so as to abut against the terminal ends of the insulationupon the leg wires furthest from the blasting cap casing. Since theinsulating material protects the leg wires from the shunt inwardlytoward the blasting cap casing and the shunt protects the blasting capfrom the point of its application, outwardly the electric blasting capshunted according to this invention cannot be exploded by stray currentbecause no difference in potential can be created between the two legwires. Additionally, the shunt may be applied away from the insulationon the terminal ends of the leg wires and still provide a great amountof safety against accidental firing.

When it is desired to remove the present kinked coil shunt from the legwires of a blasting cap, it may be stripped longitudinally from the legwires. Such stripping of the kinked coiled shunt tends to clean theuninsulated leg wires so as to provide for good contact to a suitableelectric source for initiation purposes.

The uniqueness of the present invention will be apparent from thefollowing description of the invention taken in connection with theaccompanying drawings which illustrate specific embodiments wherein:

FIG. 1 is an enlarged fragmentary side view of a shunt of this inventionapplied on lead wires of an initiator.

FIG. 2 is an enlarged fragmentary side view of a modified application ofthe present shunt on lead wires of an initiator.

FIG. 3 is a cross-sectional view of the shunts applied in FIG. 1 andFIG. 2 along the lines AA.

FIG. 4 is a cross-sectional view of the shunts applied in FIG. 1 andFIG. 2 along the lines B-B.

FIG. 5 is a side elevation of an electric blasting cap with connectinglead wires having a kinked wire shunt applied thereto.

Referring now to the drawings in which like numerals are employed todesignate like parts throughout the numeral 11 refers to an electricblasting cap assembly comprising blasting cap 13 and copper leg wire 15arid 15. Leg wires 15 and 15' are covered with an insulating material 17and 17' except for the terminal portions which are not insulated. A coilof conductive wire 19 is placed around the uninsulated ends of leg Wires15 and 15, and kinked in position as shown alternatively in FIG. 2 andFIG. 3. Several points of contact between the leg wires 15 and 15 andshunt 19 as applied in FIG. 1 and FIG. 2 are indicated in FIGS. 3 and 4as 25, 27, 29 and 31. However, the shunt of the present invention may bekinked or offset in any configuration so long as the shunt is kinked toinsure adequate contact and locking in position.

What is claimed is:

A safety device for an electric initiator which comprises incombination, leg wires having uninsulated end portions and a shunt ofcoiled wire, said shunt of coiled wire disposed about a length of saidend portions and offset in a kinked configuration therewith to insureadequate contact and locking in position.

'4 References Cited UNITED STATES PATENTS 1,606,418 11/1926 Grant 102-281,639,906 8/1927 Steers 102-28 FOREIGN PATENTS 336,423 10/1930 GreatBritain.

10 BENJAMIN A. BORCHELT, Primary Examiner.

SAMUEL FEINBERG, Examiner.

V. R. PENDEGRASS, Assistant Examiner.

